Pop up prism lens assembly

ABSTRACT

A pop up prism camera ( 10 ) having a pop up prism lens assembly ( 11 ). A first lens assembly ( 14 ), a second lens assembly ( 18 ), and a prism assembly ( 21 ) are moved in relationship to a camera housing ( 12 ) controlled by a cam tube ( 20 ). The prism assembly ( 21 ) projects outside the camera housing ( 12 ) when the pop up prism camera ( 10 ) is in an operational configuration. A prism ( 100 ) of the prism assembly ( 21 ) redirects an optical path ( 48 ). A non-angled portion ( 44 ) of a first cam groove ( 30 ) causes the prism assembly ( 21 ) to remain fixed relative to the camera housing ( 12 ) while continued rotation of the cam tube ( 20 ) allows the first lens assembly ( 14 ) and the second lens assembly ( 18 ) to continue to move to accomplish a lens zoom function.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of camera devicesand lens assemblies therefor, and more particularly to a novelconcealable lens assembly for use primarily in digital cameras. Thepredominant current application for the inventive pop up prism lensassembly is in the production of high quality digital cameras, whereinsmall size, rugged construction and cost are all important factors.

2. Description of the Background Art

It is known in the art to use one or more prisms to redirect the opticalpath in a camera. Among other advantages, the use of a prism oftenallows the designer to make the camera package more compact than anentirely linear optical path would permit. Since positioning of theprism in relation to other lens components is critical in a high qualitycamera, it has been thought that the prism should be rigidly affixedwithin the camera housing. Also, it is believed that, prior to thepresent invention, there has been no apparent advantage in causing theprism to be movable within the camera housing.

It is also known in the prior art to provide a means to manually and/orautomatically cover a camera lens when it is not in use. Usually, thismeans has included some sort of lens cap. Modern innovations inelectronic cameras have included lenses which automatically retract whenthe camera is turned off, and this sort of arrangement is oftenaccompanied by some sort of automatic closure mechanism which covers theopening into which the lens retracts.

It is also known in the prior art to use a drum type cam device to movelenses, as needed, within a camera. U.S. Pat. No. 6,670,989, issued toKawanishi, et al., teaches an example of such a device.

It would be advantageous to have a method and or means to protect thelens of a camera, when it is not is use, which contributes to making thecamera smaller and lighter, rather than requiring extra components andthereby making the camera larger, heavier, and more expensive toconstruct. It would also be advantageous to have a method and or meansto protect the lens of a camera when it is not is use which provides areliable relationship between surfaces of optical components in the lenssystem. It would also be advantageous to have a camera apparatus whichwould be simpler, more rugged, less expensive and/or optically superiorto known prior art devices.

To the inventor's knowledge, no prior art device has successfullyachieved the above described objectives. All prior art apparatus forretracting and/or protecting lens assemblies have negatively contributedto the size, weight and/or complexity of the camera, or else have notbeen as rugged and reliable as might be desired. All prior art apparatusfor bringing camera optics into a “ready” position and/or forpositioning a telephoto lens element have required relatively complex,large and expensive mechanisms, and a separate mechanism has beenrequired to perform each of these functions.

SUMMARY

Accordingly, it is an object of the present invention to provide acamera lens apparatus which is well protected when the camera is not inuse.

It is another object of the present invention to provide a camera lensapparatus which is quick and easy to bring into operational positionfrom a stored position.

It is yet another object of the present invention to provide a cameralens apparatus which is quick and easy to put into a stored positionfrom an operational position.

It is still another object of the present invention to provide a cameralens apparatus which is compact in size and light in weight.

It is yet another object of the present invention to provide a cameralens apparatus which is rugged and reliable in operation.

It is still another object of the present invention to provide a cameralens apparatus which is relatively inexpensive to manufacture.

It is yet another object of the present invention to provide a cameralens apparatus which provides a high degree of protection to opticalcomponents when the lens apparatus is in a stored position.

It is still another object of the present invention to provide a cameralens apparatus which provides a consistent and accurate associativerelationship between the optical components thereof.

Briefly, an example of the present invention has an objective lensassembly which moves in and out of a camera by the rotation of a drumcam apparatus. Movement of the objective lens assembly is along aplurality of guide rods. At the distal end of the objective lensassembly a prism redirects the optical path. The prism is positionedsuch that, when the objective lens assembly and attached prism arewithdrawn into the camera, the only surface of the prism which isexposed to the exterior is the one surface that is not in the opticalpath of the camera. Optionally, an additional cover can be affixed tothe prism which occludes an opening into which the prism retracts.Movement of the optical lens components and the prism is controlled bythe rotation of a drum type cam apparatus. Provision is made in theshape of cam grooves such that the prism can come into a fulloperational position and stay there even as the cam continues to rotateto provide a telescopic zoom function in the lens components. Accordingto a described embodiment of the invention, the cam is generallycomprised of two longitudinally divided portions, one of which serves toselectively bring the camera optics into a “ready” position and toreturn the optics to a stored position. The other cam portion serves tohold certain portions of the optics in the ready position while othercertain portions are selectively moved to change the lens systemmagnification factor, as desired by the user.

These and other objects and advantages of the present invention willbecome clear to those skilled in the art in view of the description ofmodes of carrying out the invention, and the industrial applicabilitythereof, as described herein and as illustrated in the several figuresof the drawing. The objects and advantages listed or discussed hereinare not an exhaustive list of all possible objects or advantages of theinvention. Moreover, it will be possible to practice the invention evenwhere one or more of the intended objects and/or advantages might beabsent or not required in the application.

Further, those skilled in the art will recognize that variousembodiments of the present invention may achieve one or more, but notnecessarily all, of the above described objects and/or advantages.Accordingly, the objects and advantages listed and/or discussed hereinare not essential elements of the present invention, and should not beconstrued as limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional side elevational view of acamera having an example of the inventive pop up prism lens assemblyaccording to the present invention, showing the device in a openedposition;

FIG. 2 is a diagrammatic perspective view of the pop up prism lensassembly of FIG. 1 showing the lens assembly in a ready position;

FIG. 3 is a diagrammatic perspective view of the pop up prism lensassembly of FIGS. 1 and and 2 showing the lens assembly in a closedposition; and

FIG. 4 is a diagrammatic cross-sectional side elevation view of acamera, similar to the view of FIG. 1 except that the device is shown ina closed position.

DETAILED DESCRIPTION OF THE INVENTION

This invention is described in the following description with referenceto the Figures, in which like numbers represent the same or similarelements. While this invention is described in terms of modes forachieving the objectives of this invention, it will be appreciated bythose skilled in the art that variations may be accomplished in view ofthese teachings without deviating from the spirit or scope of thepresent invention. The embodiments and variations of the inventiondescribed herein, and/or shown in the drawings, are presented by way ofexample only and are not limiting as to the scope of the invention.Unless otherwise specifically stated, individual aspects and componentsof the invention may be omitted or modified, or may have substitutedtherefore known equivalents, or as yet unknown substitutes such as maybe developed in the future or such as may be found to be acceptablesubstitutes in the future. The invention may also be modified for avariety of applications while remaining within the spirit and scope ofthe claimed invention, because the range of potential applications isgreat, and because it is intended that the present invention beadaptable to many such variations.

A known mode for carrying out the invention is a pop up prism camera.The inventive pop up prism camera 10 is depicted in a side elevationalview in FIG. 1 and is designated therein by the general referencecharacter 10. The pop up prism camera 10 includes an example of theinventive pop up prism lens assembly 11 in a camera housing 12. Thecamera housing 12 will contain additional components customary to thefunction of a camera, such as a view finder or electronic user display,operator control devices, and the like, all of which will be familiar tothose skilled in the art. Except as specifically discussed herein, suchadditional components are not relevant to the present invention and willnot be shown in the view of FIG. 1 for the sake of clarity. FIGS. 2 and3 are different perspective views of the pop up prism lens assembly 11introduced in FIG. 1, showing the pop up prism lens assembly 11 in“ready” and “closed” positions, respectively. The following descriptionof the pop up prism lens assembly 11 will be in reference to all ofFIGS. 1 through 3, since it will be desirable to view some aspects ofthe invention from all three of these views.

As can be seen in the view of FIG. 1, the pop up prism lens assembly 11has a first (distal) lens assembly 14, a field lens 15, a sensor 16 anda second (proximal) lens assembly 18. The first lens assembly 14 and thesecond lens assembly 18 are, respectively, the front and rear elementsof a telephoto lens as will be discussed in more detail hereinafter. Thesensor 16 is the electronic sensor array of the digital pop up prismcamera 10. The field lens 15 is the lens closest to the sensor 16 whichprojects an image from the pop up prism lens assembly 11 onto the sensor16. One skilled in the art will recognize that the sensor 16 can be ofessentially any type now known or yet to be developed. In the example ofFIG. 1, the sensor 16 is a CCD image sensor. It is within the scope ofthe invention that the sensor 16 could also be a photographic film, orthe like.

The first lens assembly 14 and the second lens assembly 18 move along atleast one (two in this present example) of guide rods 19 under thecontrol of a cam tube 20, as will be discussed in greater detailhereinafter. A prism assembly 21 is also movably affixed along the guiderods 19. It should be noted that mechanical apparatus for rotating thecam tube 20 is conventional in nature and is omitted from the view ofFIG. 1 for the sake of clarity. It is anticipated that the cam tube 20can be rotated either manually (e.g., a thumb-wheel), or else by anelectric motor controlled by an on/off switch and/or by a “zoom” buttonon the camera housing 12. In the example of FIGS. 1 through 3, the camtube 20 is powered through a gear assembly by a high speed electricmotor (not shown), although it is within the scope of the invention thatthe cam tube 20 could be powered by a stepper motor, or essentially anyother type of motive apparatus that might be adapted to the purpose.

The first lens assembly 14 is guided along an inner guide rod 19 a andan outer guide rod 19 b by a first guide assembly 22. A first innerguide bushing 24 of the first guide assembly 22 slidably fits over theinner guide rod 19 a, and a first outer guide bushing 26 of the firstguide assembly 22 slidably fits over the outer guide rod 19 b. A firstcam follower 28 fits into and follows a first cam groove 30 in the camtube 20.

The second lens assembly 18 is guided along the inner guide rod 19 a andthe outer guide rod 19 b by a second guide assembly 32. A second innerguide bushing 34 of the second guide assembly 32 slidably fits over theinner guide rod 19 a, and a second outer guide bushing 36 of the secondguide assembly 32 slidably fits over the outer guide rod 19 b. A secondcam follower 38 fits into and follows a second cam groove 40 in the camtube 20.

The prism assembly 21 is guided along the inner guide rod 19 a and theouter guide rod 19 b by a third guide assembly 42. A third inner guidebushing 44 of the third guide assembly 42 slidably fits over the innerguide rod 19 a, and a third outer guide bushing 46 of the third guideassembly 42 slidably fits over the outer guide rod 19 b. A third camfollower 48 fits into and follows a third cam groove 50 in the cam tube20.

As can be appreciated in light of the foregoing description of the popup prism camera 10, it can be seen that the first lens assembly 14selectively moves toward or away from the sensor 16 as the cam tube 20is rotated, and further that the second lens assembly 18 alsoselectively moves toward or away from the sensor 16 as the cam tube 20is rotated. As can also be seen by comparing the views of FIGS. 1through 3, the third cam groove 50 has an angled portion 52 (FIG. 1) anda non-angled portion 54 (FIGS. 2 and 3). Accordingly, as the third camfollower 48 moves along angled portion 52 of the third cam groove 50 theprism assembly 21 will move inward and outward as described above.However, when the third cam follower 48 reaches the non-angled portion54 of the third cam groove 50 then, even though the cam tube 20 maycontinue to rotate, the prism assembly 21 will remain relatively fixedin relationship to the camera housing 12. Note that a small portion ofthe angled portion 52 of the third cam groove, with the third camfollower 48 therein, can also be seen in the view of FIG. 3.

As can be seen in the view of FIG. 1, the second cam groove 40 also hasa non-angled portion 54 a such that the second lens assembly 18 willstop advancing along the rear movement arrow 62 even as the cam tube 20continues to rotate when the second cam follower 38 is in that portionof the second cam groove 40. This will tend to prevent the second lensassembly 18 from coming to an abrupt halt as the second lens assembly 18reaches what would otherwise be the end of the second cam groove 40.

Similarly, as the cam tube 20 is rotated, the first lens assembly 14will selectively move into an operational position (as depicted in FIGS.1 and 2) with the prism assembly 21. Also, as the cam tube 20 continuesto rotate, the second lens assembly 18 will selectively move toward oraway from first lens assembly 14 to accomplish the zoom function. In theexample of the invention presently described, the movement of the secondlens assembly 18 relative to the first lens assembly 14 will accomplishapproximately a fourfold change in the magnification power of the pop upprism lens assembly 11, otherwise known as a 4× zoom function. Oneskilled in the art will recognize that coordinated movement of both thefirst lens assembly and the second lens assembly 18 relative to botheach other and to the fixed field lens 15 will accomplish the zoomfunction while keeping the image focused on the sensor 16. As can alsobe seen by a comparison of the views of FIGS. 1 through 3, in thisembodiment of the invention, the first cam groove is 30 more greatlyelongated along the length of the cam tube 20 than is the second camgroove 40 such that, as the cam tube 20 is rotated, the first lensassembly 14 will move a greater distance than will the second lensassembly 18.

Focus of the pop up prism lens assembly 11 can optionally beaccomplished by rotating a focus ring 56 (FIG. 1). The focus ring 56 isnot significantly different from similar mechanisms in prior artdevices. The focus ring 56 can, optionally, be moved manually (via anoptional manual adjustment mechanism, not shown) or else the focus ring56 can be rotated by an electric motor controlled by a focus control onthe exterior of the camera housing 12.

Also shown in the view of FIG. 1 is an optical path 58 along which lighttravels through the prism assembly 21, through the first lens assembly14, through the second lens assembly 18, through the field lens 15 andinto the sensor 16. As previously described, movement of the first lensassembly 14 will be inward and outward as indicated by a front movementarrow 60, and movement of the second lens assembly 18 will be inward andoutward as indicated by a rear movement arrow 62.

As can be appreciated in light of the above discussion, the pop up prismcamera 10 is depicted in the view of FIG. 1 in an opened (ready)position, with the prism assembly 21 generally outside the limits of thecamera housing 12. FIG. 4 is a diagrammatic cross sectional sideelevational view of the pop up prism camera 10, similar to the view ofFIG. 1, except that the camera 10 is depicted in the view of FIG. 4 in astored (closed) position with the prism assembly 21 generally inside thelimits of the camera housing 12, and further with the first lensassembly 14 and the second lens assembly 18 drawn relatively near toeach other.

In the view of FIG. 3 it can be seen that the prism assembly 21 has aprism 100 which is protected by prism housing 102. When the prismassembly 21 is withdrawn into the camera housing 12 (FIG. 4) then theprism housing 102 generally occludes an opening 104 in the camerahousing 12 through which the prism assembly 21 can be moved to projectoutside the camera housing 12, thereby protecting the prism 100 andfurther preventing foreign objects from entering into the camera housing12.

Referring now to the view of FIG. 2, it can be seen that, in theembodiment of the invention described, the cam tube 20 has a firstoperational portion 110 and a second operational portion 112, each ofwhich, in this presently described embodiment, occupy approximately halfof the circumference of the cam tube 20. Of course, the slope of the camgrooves 30, 40 and 50 could be made greater, such that less than a full360 degree rotation of the cam tube 20 would be required to move throughthe entire operational range thereof. In such an embodiment, each of thefirst operational portion 110 and the second operational portion 112would take up generally less than half of the circumference of the camtube 30. Similarly, the slope of the cam grooves 30, 40 and 50 could bemade such that more than one full rotation of the cam tube 20 would berequired to move the pop up prism lens assembly 11 through its entireoperational range. In such an example, the first operational portion 110and the second operational portion 112 would overlap about thecircumference of the cam tube. These are but some of the possiblevariations in the shape of the cam tube 20 and the cam grooves 30, 40and 50 thereon, which might be employed to adapt the invention to aparticular application. In any of these configurations, it is an aspectof the present invention that there will be a portion of the cam tube 20such that, when the cam followers 28, 38 and 48 follow therein, then theelements of the pop up prism lens assembly will be brought into the“ready” position, as described above. Further, there will be a portionof the cam tube 20 such that, when the cam followers 28, 38 and 48follow there, then the prism assembly 21 will remain in the “ready”position while other elements of the pop up prism lens assembly 11continue to move, as required, to change the lens configuration (such asto change the magnification factor, as described herein).

In the view of FIG. 3 it can also be seen that, to save space andweight, the cam tube 20 can be made such that it has a hollow center120. In such an application, the hollow center 120 can optionally beused to house a battery 122, a flash capacitor (not shown) or othercamera components, as required.

Various modifications may be made to the invention without altering itsvalue or scope. For example, the sizes, shapes and quantities ofcomponents shown and described in relation to the examples discussedherein could each or all be varied according the needs or convenience ofa particular application.

All of the above are only some of the examples of available embodimentsof the present invention. Those skilled in the art will readily observethat numerous other modifications and alterations may be made withoutdeparting from the spirit and scope of the invention. Accordingly, thedisclosure herein is not intended as limiting and the appended claimsare to be interpreted as encompassing the entire scope of the invention.

INDUSTRIAL APPLICABILITY

The inventive pop up prism camera 10 and associated pop up prism lensassembly 11 is intended to be widely used for a variety of cameraapplications. A particular use is for mid-priced digital cameras whereincompact size, durability, picture quality, and economy are all importantfactors.

According to the presently contemplated embodiments of the presentinvention, the cam tube 20 does take up a significant amount of space.However, that space is fully utilized in that additional components,such as a battery, a capacitor for flash applications or the like, canoptionally be fitted within the cam tube 20.

The inventive apparatus as described herein has the advantage that itdoes not introduce parallax into the optical path during the zooming ofthe pop up prism lens assembly 11. Further, the apparatus describedcontributes to the creation of a small camera in that the length andoverall size is minimal, and further contributes to the creation of aninexpensive and reliable camera in that the quantity of movingcomponents is minimized.

Since the pop up prism lens assemblies 11 of the present invention maybe readily produced and integrated with existing camera sensor anddigital camera image capture and storage systems, and since theadvantages as described herein are provided, it is expected that it willbe readily accepted in the industry. For these and other reasons, it isexpected that the utility and industrial applicability of the inventionwill be both significant in scope and long-lasting in duration.

1. A camera, comprising: a sensor array; a prism affixed within thecamera such that the prism moves selectively into and out of the camerasuch that the prism directs an optical path toward the sensor array whenthe prism is moved out of the camera; and a proximal portion of a lensassembly that can be selectively moved toward and away from the sensorarray; and wherein the prism is caused to move by a generally drumshaped cam; and movement of the prism follows a generally spiral featureon the cam.
 2. The camera of claim 1, wherein: at least a portion of theoptical path is generally perpendicular to the sensor array.
 3. Thecamera of claim 1, and further including: a prism housing that at leastpartially encloses the prism.
 4. The camera of claim 1, wherein:movement of the proximal portion of the lens assembly changes themagnification of the lens assembly.
 5. The camera of claim 1, wherein:both the proximal portion of the lens assembly and a distal portion ofthe lens assembly are caused to move by the cam.
 6. The camera of claim5, wherein: movement of the proximal portion and the distal portion ofthe lens assembly follow the generally spiral feature on the cam.
 7. Thecamera of claim 6, wherein; the generally spiral feature includes atleast one groove; and at least one follower projection is affixed to thelens assembly to cause movement or at least one portion of the lensassembly as the follower follows the generally spiral feature.
 8. Thecamera of claim 5, wherein: the generally spiral feature hats anon-advancing portion such that one of the proximal portion of the lensor the distal portion of the lens will cease to advance while the othercontinues to advance as the cam is rotated.
 9. The camera of claim 1,wherein; the generally spiral feature includes at least one groove; andat least one follower projection is affixed to the prism to causemovement of the prism as the follower follows the generally spiralfeature.
 10. The camera of claim 1, wherein: at least a portion of thegenerally spiral feature has a non-advancing portion such that the prismwill cease to advance when the prism reaches the non-advancing portioneven as the cam continues to rotate.
 11. A camera, comprising: animaging medium; a lens apparatus for directing an optical path onto theimaging medium; and a prism for directing the optical path onto the lensapparatus; and a motive apparatus for moving the prism and furthermoving at least a portion of the lens apparatus; and wherein the motiveapparatus includes a cam; the cam has at least two contoured features;movement of the prism is controlled by a first one of the contouredfeatures; and movement of a least a portion of the lens apparatus iscontrolled by a second one of the contoured features.
 12. The camera ofclaim 11, wherein: moving at least a portion of the lens apparatuscauses a change in the magnification factor of the lens apparatus. 13.The camera of claim 11, wherein the motive apparatus includes: a drumcam; and a follower for following a feature of the drum cam.
 14. Thecamera of claim 13, wherein: the feature is a groove in the cam; and acam follower fits within the groove such that the cam follower movesgenerally along at least a portion of the length of the cam as the camis rotated.
 15. The camera of claim 11, wherein: the imaging medium is adigital sensor.
 16. The camera of claim 11, wherein: the contouredfeature includes a groove in the cam.
 17. The camera of claim 11,wherein: the cam is a drum type cam.
 18. The camera of claim 11,wherein: the cam has a first portion such that rotation of the camthrough the first portion causes the prism to come into a readyposition; and the cam has a second portion such that rotation of the camthrough the second portion causes the prism to remain generallystationary while at least a portion of the lens apparatus moves.
 19. Thecamera of claim 18, wherein: the earn is a drum type cam; and said firstportion and said second portion each include at least a portion of thecircumference of the drum type cam.
 20. The camera of claim 18, wherein:the cam is a drum type cam; and said first portion is located generallyabout a first half of the circumference of the cam; and said secondportion is located generally about a second half of the circumference ofthe cam.
 21. The camera of claim 11, wherein: the first contouredfeature includes a non-advancing portion such that the prism remainsgenerally stationary while a earn follower affixed to the prism iswithin the non-advancing portion.
 22. The camera of claim 21, wherein:the second contoured feature further includes a second non-advancingportion, such that at least a portion of the lens apparatus remainsgenerally stationary while a cam follower affixed to that portion of thelens apparatus is within the second non-advancing portion.
 23. A camera,comprising; a sensor array; and a prism affixed within the camera suchthat the prism is caused to move by a cam selectively into and out ofthe camera such that the prism directs an optical path toward the sensorarray when the prism is moved out of the camera; and wherein the cam isgenerally drum shaped; and movement of the prism follows a generallyspiral feature on the cam.
 24. The camera of claim 23, wherein; thegenerally spiral feature includes at least one groove; and at least onefollower projection is affixed to the prism to cause movement of theprism as the follower follows the generally spiral feature.
 25. Thecamera of claim 23, wherein: at least a portion of the generally spiralfeature has a non-advancing portion such that the prism will cease toadvance when the prism reaches the non-advancing portion even as the camcontinues to rotate.
 26. A camera, comprising: an imaging medium; a lensapparatus for directing an optical path onto the imaging medium; and aprism for directing the optical path onto the lens apparatus; and amotive apparatus for moving the prism, the motive apparatus including acam; and wherein the cam has at least two contoured features; movementof the prism is controlled by a first one of the contoured features; andmovement of at least a portion of the lens apparatus is controlled by asecond one of the contoured features.
 27. The camera of claim 26,wherein: the motive apparatus further moves at least a portion of thelens apparatus.
 28. The camera of claim 27, wherein: moving at least aportion of the lens apparatus causes a change in the magnificationfactor of the lens apparatus.
 29. The camera of claim 26, wherein: themotive apparatus includes a drum cam and a follower for following afeature of the drum cam.
 30. The camera of claim 29, wherein: thefeature is a groove in the drum cam; and a cam follower fits within thegroove such that the earn follower moves generally along at least aportion of the length of the cam as the cam is rotated.
 31. The cameraof claim 26, wherein: the imaging medium is a digital sensor.
 32. Thecamera of claim 26, wherein: the contoured feature includes a groove inthe cam.
 33. The camera of claim 26, wherein: the cam is a drum typecam.
 34. The camera of claim 26, wherein: the cam has a first portionsuch that rotation of the cam through the first portion causes the prismto come into a ready position; and the cam has a second portion suchthat rotation of the cam through the second portion causes the prism toremain generally stationary while at least a portion of the lensapparatus moves.
 35. The camera of claim 34, wherein: the cam is a drumtype cam; and said first portion and said second portion each include atleast a portion of the circumference of the drum type cam.
 36. Thecamera of claim 34, wherein: the cam is a drum type cam; and said firstportion is located generally about a first half of the circumference ofthe cam; and said second portion is located generally about a secondhalf of the circumference of the cam.
 37. The camera of claim 26,wherein: the first contoured, feature includes a non-advancing portionsuch tat the prism remains generally stationary while a cam followeraffixed to the prism is within the non-advancing portion.
 38. The cameraof claim 37, wherein: the second contoured feature further includes asecond non-advancing portion, such that at least a portion of the lensapparatus remains generally stationary while a cam follower affixed tothat portion of the lens apparatus is within the second non-advancingportion.